.TH softirqs 8  "2015-10-20" "USER COMMANDS"
.SH NAME
softirqs \- Measure soft IRQ (soft interrupt) event time. Uses Linux eBPF/bcc.
.SH SYNOPSIS
.B softirqs [\-h] [\-T] [\-N] [\-C] [\-d] [\-c CPU] [interval] [count]
.SH DESCRIPTION
This summarizes the time spent servicing soft IRQs (soft interrupts), and can
show this time as either totals or histogram distributions. A system-wide
summary of this time is shown by the %soft column of mpstat(1), and soft IRQ
event counts (but not times) are available in /proc/softirqs.

This tool uses the irq:softirq_enter and irq:softirq_exit kernel tracepoints,
which is a stable tracing mechanism. BPF programs can attach to tracepoints
from Linux 4.7 only. An older version of this tool is available in tools/old,
and uses kprobes instead of tracepoints.

Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bcc.
.SH OPTIONS
.TP
\-h
Print usage message.
.TP
\-T
Include timestamps on output.
.TP
\-N
Output in nanoseconds.
.TP
\-C
Show the number of soft irq events.
.TP
\-d
Show IRQ time distribution as histograms.
.TP
\-c CPU
Trace on this CPU only.
.SH EXAMPLES
.TP
Sum soft IRQ event time until Ctrl-C:
#
.B softirqs
.TP
Show the number of soft irq events:
#
.B softirqs \-C
.TP
Show soft IRQ event time as histograms:
#
.B softirqs \-d
.TP
Print 1 second summaries, 10 times:
#
.B softirqs 1 10
.TP
1 second summaries, printed in nanoseconds, with timestamps:
#
.B softirqs \-NT 1
.TP
Sum soft IRQ event time on CPU 1 until Ctrl-C:
#
.B softirqs \-c 1
.SH FIELDS
.TP
SOFTIRQ
The kernel function name that performs the soft IRQ action.
.TP
TOTAL_usecs
Total time spent in this soft IRQ function in microseconds.
.TP
TOTAL_nsecs
Total time spent in this soft IRQ function in nanoseconds.
.TP
usecs
Range of microseconds for this bucket.
.TP
nsecs
Range of nanoseconds for this bucket.
.TP
count
Number of soft IRQs in this time range.
.TP
distribution
ASCII representation of the distribution (the count column).
.SH OVERHEAD
This traces kernel functions and maintains in-kernel counts, which
are asynchronously copied to user-space. While the rate of interrupts
be very high (>1M/sec), this is a relatively efficient way to trace these
events, and so the overhead is expected to be small for normal workloads, but
could become noticeable for heavy workloads. Measure in a test environment
before use.
.SH SOURCE
This is from bcc.
.IP
https://github.com/iovisor/bcc
.PP
Also look in the bcc distribution for a companion _examples.txt file containing
example usage, output, and commentary for this tool.
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHORS
Brendan Gregg, Sasha Goldshtein, Rocky Xing
.SH SEE ALSO
hardirqs(8)
